In the field of orthodontics, the archwire is attached to an orthodontic bracket which in turn is cemented or otherwise attached to a patient's tooth. A precise slot is formed in the center portion of the bracket through which the archwire passes. The archwire is cylindrical or quadrilateral in shape to fit into the corresponding slot in the bracket. Historically, the archwire has been fastened to the bracket by means of ligature wires. Over time and after multiple tightening or replacement procedures, the tooth gradually moves towards the archwire until complete engagement has been obtained. By this means, eventually the bracket slot is fully engaged to the archwire.
More recently, flexible archwires have been utilized which provide more rapid engagement of the archwire into the bracket slot, thereby moving individual teeth more quickly. These elastic archwires often contain nickel and titanium alloys. Another means of attaching the archwire to the bracket is by means of plastic rings called Alastics or O-rings. These rings loop around the tie wings of the bracket and thereby draw the archwire tightly to the bracket.
Also, recently a new family of orthodontic brackets was introduced which are self-ligating thereby eliminating the need for ligatures or Alastics. By this means, a movable sleeve, contained within the bracket, forces locks the archwire into the bracket slot resulting in a more rapid placement, removal and adjustment of the archwires, thereby by saving the clinician valuable time. Another advantage of the self-ligating brackets is greatly reduced friction thereby allowing the tooth to slide more easily during certain movements. This can be accomplished with reduced force and results in shorter treatment times.
Although reduced friction from the self-ligating brackets is often desirable, sometimes more friction is desired such as near the end of treatment when small adjustments in the teeth are necessary and when other teeth are utilized as stabilizing anchor units. With frictionless brackets, the desired stability is not available and, therefore, toward the end of the treatment cycle tooth movement time is extended. Another disadvantage of the self-ligating brackets is that they include moving parts which become distorted, warped or disengaged. This in turn requires clinical modifications or placement of more conventional brackets as treatment proceeds.